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Title: Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene

Abstract

The discovery of superconducting and insulating states in magic-angle twisted bilayer graphene (MATBG) has ignited considerable interest in understanding the nature of electronic interactions in this chemically pristine material. The transport properties of MATBG as a function of doping are similar to those of high-transition-temperature copper oxides and other unconventional superconductors which suggests that MATBG may be a highly interacting system. However, to our knowledge, there is no direct experimental evidence of strong many-body correlations in MATBG. Here we present high-resolution spectroscopic measurements, obtained using a scanning tunnelling microscope, that provide such evidence as a function of carrier density. MATBG displays unusual spectroscopic characteristics that can be attributed to electron–electron interactions over a wide range of doping levels, including those at which superconductivity emerges in this system. We show that our measurements cannot be explained with a mean-field approach for modelling electron–electron interactions in MATBG. The breakdown of a mean-field approach when applied to other correlated superconductors, such as copper oxides, has long inspired the study of the highly correlated Hubbard model3. We show that a phenomenological extended-Hubbard-model cluster calculation, which is motivated by the nearly localized nature of the relevant electronic states of MATBG, produces spectroscopic features that aremore » similar to those that we observed experimentally. Finally, our findings demonstrate the critical role of many-body correlations in understanding the properties of MATBG.« less

Authors:
 [1];  [2];  [1];  [1];  [1];  [3];  [3];  [1];  [1]
  1. Princeton Univ., NJ (United States). Joseph Henry Lab., and Dept. of Physics
  2. Princeton Univ., NJ (United States). Princeton Center for Theoretical Science
  3. National Inst. for Materials Science (NIMS), Tsukuba (Japan)
Publication Date:
Research Org.:
Princeton Univ., NJ (United States); National Inst. for Materials Science (NIMS), Tsukuba (Japan)
Sponsoring Org.:
USDOE
OSTI Identifier:
1574996
Grant/Contract Number:  
FG02-07ER46419; SC0016239
Resource Type:
Accepted Manuscript
Journal Name:
Nature (London)
Additional Journal Information:
Journal Name: Nature (London); Journal Volume: 572; Journal Issue: 7767; Journal ID: ISSN 0028-0836
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; electronic properties; electronic materials; superconductivity; superconducting materials; superconducting properties

Citation Formats

Xie, Yonglong, Lian, Biao, Jäck, Berthold, Liu, Xiaomeng, Chiu, Cheng-Li, Watanabe, Kenji, Taniguchi, Takashi, Bernevig, B. Andrei, and Yazdani, Ali. Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene. United States: N. p., 2019. Web. doi:10.1038/s41586-019-1422-x.
Xie, Yonglong, Lian, Biao, Jäck, Berthold, Liu, Xiaomeng, Chiu, Cheng-Li, Watanabe, Kenji, Taniguchi, Takashi, Bernevig, B. Andrei, & Yazdani, Ali. Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene. United States. doi:10.1038/s41586-019-1422-x.
Xie, Yonglong, Lian, Biao, Jäck, Berthold, Liu, Xiaomeng, Chiu, Cheng-Li, Watanabe, Kenji, Taniguchi, Takashi, Bernevig, B. Andrei, and Yazdani, Ali. Wed . "Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene". United States. doi:10.1038/s41586-019-1422-x.
@article{osti_1574996,
title = {Spectroscopic signatures of many-body correlations in magic-angle twisted bilayer graphene},
author = {Xie, Yonglong and Lian, Biao and Jäck, Berthold and Liu, Xiaomeng and Chiu, Cheng-Li and Watanabe, Kenji and Taniguchi, Takashi and Bernevig, B. Andrei and Yazdani, Ali},
abstractNote = {The discovery of superconducting and insulating states in magic-angle twisted bilayer graphene (MATBG) has ignited considerable interest in understanding the nature of electronic interactions in this chemically pristine material. The transport properties of MATBG as a function of doping are similar to those of high-transition-temperature copper oxides and other unconventional superconductors which suggests that MATBG may be a highly interacting system. However, to our knowledge, there is no direct experimental evidence of strong many-body correlations in MATBG. Here we present high-resolution spectroscopic measurements, obtained using a scanning tunnelling microscope, that provide such evidence as a function of carrier density. MATBG displays unusual spectroscopic characteristics that can be attributed to electron–electron interactions over a wide range of doping levels, including those at which superconductivity emerges in this system. We show that our measurements cannot be explained with a mean-field approach for modelling electron–electron interactions in MATBG. The breakdown of a mean-field approach when applied to other correlated superconductors, such as copper oxides, has long inspired the study of the highly correlated Hubbard model3. We show that a phenomenological extended-Hubbard-model cluster calculation, which is motivated by the nearly localized nature of the relevant electronic states of MATBG, produces spectroscopic features that are similar to those that we observed experimentally. Finally, our findings demonstrate the critical role of many-body correlations in understanding the properties of MATBG.},
doi = {10.1038/s41586-019-1422-x},
journal = {Nature (London)},
number = 7767,
volume = 572,
place = {United States},
year = {2019},
month = {7}
}

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